In general, a liquid crystal display device that is a representative example of a display device requires an illumination device disposed on a side of a liquid crystal display panel that displays images opposite to a display surface of the liquid crystal display panel, that is, the backside of the liquid crystal display panel because the liquid crystal display panel itself does not emit light. The illumination device radiates light toward the liquid crystal display panel that is an object to be irradiated, so that the liquid crystal display device can display images on a screen thereof. Such an illumination device that is to be disposed on the backside of a display surface of a liquid crystal display panel as described above is called, for example, a backlight unit.
For example, a cold-cathode fluorescent lamp and an LED (a light-emitting diode) are well-known examples of a light source used in such a backlight unit. The illumination methods used in such a backlight unit are mainly divided into two types: a direct-type illumination method and an edge-light type illumination method. In a direct backlight unit, a plurality of light sources are disposed directly under a liquid crystal display panel, that is, in a region facing the rear surface of the liquid crystal display panel. In an edge-light backlight unit, a light guide plate having approximately the same size as that of a surface of a liquid crystal display panel is disposed behind the liquid crystal display panel, and a light source is disposed in an edge portion of the light guide plate, so that the light guide plate causes light of the light source having a linear shape to be emitted in a planar form.
PTL 1 discloses an example of such a backlight unit of the related art and an example of such an illumination device of the related art. The backlight device described in PTL 1 includes light sources, a case in which the light sources are to be accommodated, suction ports and suction fans that draw outside air into the case, discharge ports and discharge fans that discharge air in the area inside the case to the outside, and cooling fans that lower the temperature inside the case. A large number of the suction ports and the suction fans, the discharge ports and the discharge fans, and the cooling fans are provided, so that temperature deviation inside the case is minimized, and an increase in the temperature due to the light sources is suppressed.